The ability to time underlies adaptive behavior. Precise motor behavior is carefully timed. Decisions about whether or not to take an action depend on knowledge of when they are appropriate. Memories for how long actions usually take underlies most ordinary activity such as planning a day or knowing how long it takes to cross a street. This learning of time is automatic and a foundation of behavioral organization. The purpose of this grant is to understand how times are learned, remembered and used to guide behavior. We explore the psychological and biological mechanisms that govern both when we make a response at the right time and those that govern our ability to withhold a response when it is the wrong time. These processes are studied in animal models that allow us to observe and alter the functioning of the cortico-striatal- thalamo- cortical brain circuits that underlie these capacities. In particular, we are interested in how dopamine signaling in these circuits conveys information about time. Disordered timing and deficits in the capacity to anticipate predictable events are associated with a number of psychiatric disorders including attention deficit hyperactivity disorder, schizophrenia and depression. The diminished capacity to anticipate future consequences also play a role in substance abuse disorders. Distortions in timing and anticipation are both a symptom of the disorders as well as a source of additional problems. Understanding these basic mechanisms will lead to new treatment strategies and targets for a wide range of psychiatric disorders and human problems.